Reheating method and furnace



Nov. 19, 1940. 4H. PUPPE 2,222,372

REHEATING lMETHQD AND FURNACE Filed Oct. 6, 1936 Patented Nov. 19, 1940 UNITED STATES PATENT OFFICE Application October 6, 1936, Serial No. 104,285 In Germany October 11, 1935 y 1 Claim.

This invention relates firstly to an improved reheating method for the manufacture' of long rolled profiled pieces of any desired sectional shape, for instance such as bars, wires, and the 5 like, and secondly to an improved reheating furnace for carrying out that method.

When rolling bars, billets and profiled pieces of any kind the rolling material gradually cools down so that reheating in a rolling mill furnace to the proper rolling temperature is required if billets of large sectional area are to be rolled down, 'for instance to rods or wires of small sectional area. Particularly long pieces do not cool down uniformly along their entire length, but the front portion, i. e. the end to be rolled first as a rule cools down less than the other or rear portion. When rolling wire, for instance, the front end of the roughened billet, leaving the furnace with a uniform temperatur along its entire 520 length, is passed to and fro me hanically through the roughing train of rolls i quick succession, whereas the end of the wire due to the continuous decrease in diameter reaches the passes in increasing periods of time. Consequently congiven to this rear end of the wire than to the front end. The difference between the temperatures at the commencement of the rolling procedure and on leaving the last pass may amount to 150 C. even to 200 C. Naturally due to the temperature differences the rolling of the hotter front end of the material is carried out under condi-I tions fundamentally diiferent from those of the cooler rear portions which, with most kinds of steel, is accompanied by detrimental consequences as to strength, hardenability and the like.

The object of the present invention is to obviate the above-mentioned drawbacks in a simple manner and with simple means, and I attain the intermediate heating which takes placeprior to the nish rolling to such a higher. temperature at those portions which cool down quicker during the finish rolling that in the finish pass the material is of substantial uniform temperature along, its entire length. i

Hitherto attention has been paid solely to heating the material to be rolled as uniformly as possible in the reheating furnace. In contradistinction .thereto in the method according to the invention, the rear end portions of billets are, if such billets are to be rolled to wires, heated more strongly than the front portions or heads of thel same which are first introduced into the rolling mill passes.

siderably much more time for' cooling down is v object in view by heating the material during the This non-uniform heating can be carried out in' a simple manner in a gas-fired furnace, as Well as in an electrically heated one. In the first-mentioned type of furnaces, or in equivalent furnaces fired with liquid or solid fuel, rows of 6 regulable burners are provided in the longitudinal direction of the material to be heated, say billets etc. whereas in the case of electric furnaces rows of resistances are provided which can be diferently loaded. l

The differences of temperature to be brought about in the furnace between the several zones, extending at right angles with respect to the longitudinal direction of the billets etc. to be .conveyed through the furnace, must be regulated in accordance with the particular kind of the rolling procedure, because'they depend on the rolling speed, the number -of the passes, the reduction` of the sectional area, the length of the billet and the finished profile respectively, as well as the local conditions andthe outer temperature. The regulation can easily be effected by observing the temperatures of the individual longitudinal portions of a rolled pro ,.Wire orthe like on leaving the finishing groove I, he observer may then regulate the differences/ of temperature between the various zones inthe reheating furnace by remote adjustment of the burners or of the resistances until the finished profile is of uniform temperature along its entire length. Au- 30 tomatically operating devices may, however, also .be used for regulating the burners orthe resistances. Thus, for instance, photo-cells, pyrometers or the like, inuencing the control mem- `bers of the heating devices, may be employed through which the rolled pieces are conducted at the las't pass.

The use of the aboye-described method er1- sures a uniformvtemperature of the rolled piece along its entire length, resulting in obtaining a uniform quality, strength, and grade of hardeng. The method according to the invention can be carried out, for instance, .with the aid 0f the furnace illustrated diagrammatically and by way of example in the accompanying drawing which shows in perspective a transverse section through the furnace the rear portion of which being omitted.

In this drawing, 2 denotes a. lateral aperture in the furnace wall through which the reheated .pieces 3 (shown as bars in this case) are conveyed in the direction of the arrow to .the rolling mill (not shown) by suitable means (likewise not shown). The bars 3 are supported side by side 55 by longitudinal bars constituting in their entirety a sort of grate, extending over .the entire length of the furnace.

Arranged in the longitudinal direction of the furnace below and above the grate 4 respectively are burners 5, 6,1, 8, 9 and I0 and II, I2,

I3, I6, I5 and I6 respectively which extend verti-4 cally to the longitudinal axis of the material to be heated. Nozzles I1 and I8 respectively direct-y ing the flames against the bars 3 from below and from above project from the burners 5-II and II-II respectively. Each of the burners is prov`vided with a plurality of nozzles arranged in a Y manner, that the amount of heat supplied to the bars 3 by the burners 5--I0 and II-IG increases in the direction from the burners 5, II to the burners IEI,Y I6. By .this arrangement, the ends of lthe bars 3, which during rolling cool down quicker, are correspondingly more highly heated, resulting inrobtaining uniform temperature of all parts of the material travelling through the last pass.

What l claim is:

In a method of manufacturing long profiled pieces of relatively rigid material such as rods, Wires-and the like, the steps of heating a bar of said material to rolling temperature; subjecting the bar to preliminary rolling operations; delivering said bar to a reheating furnace; simultaneously and independently reheating a series of substantially contiguous sections along the en. tire length of said bar while maintaining it against longitudinal movement in said furnace during said reheating and wh'le regulating the temperatures .of said sections and maintaining said temperatures at such levels that the trailing portion of said bar is 'heated to an appreciably higher temperature than the leading portion with a progressive temperature gradient between said portions; and then subjecting' the reheated bar to further and nishing rolling operations.

HEINZ PUPPE. 

